Such friction wheels are well adapted to the transmission of high torques, as for example is the case with industrial vehicles, due to a balanced transmission of the torque to the damping device and equal distribution of this torque between the guide rings.
The guide rings are commonly secured to the support ring by means of rivets passing through the latter: this arrangement is disclosed in United Kingdom published patent specification GB 2 183 787A, which in this respect repeats the arrangements disclosed in German Utility Model specification DE-U-1 840 718 and its corresponding U.S. Pat. No. 3,203,205. These rivets, the number of which is limited, and which concentrate stresses locally, constitute weak points of the assembly. In order to minimize this disadvantage, their length can only be reduced to the detriment of the axial length of the support ring, and therefore also of the axial length of the loose coupling means provided between the support ring and the hub.
This can then have the effect of limiting the magnitude of the torque which can be transmitted. In addition, the rivets occupy radial space, and this is again detrimental to the loose coupling means between the support ring and the hub, and therefore also to the transmissible torque.
Another disadvantage of the rivets is that they do not lend themselves to easy fitting of the predamper device.
It is also known, from the French published patent specification FR 2 570 147A and the corresponding U.S. Pat. No. 4,688,666, to provide an arrangement which does in fact facilitate such fitting, and in which the predamper device and the hub together constitute a sub-assembly. However, in this arrangement as disclosed in the said French patent specification 2 570 147, the friction disc is fixed to the guide rings despite the fact that the damper plate is fixed to the support ring, and the damping device is inserted axially between the damper plate and one of the guide rings. This makes the assembly difficult to dismantle.
Dismantling can be a requirement, for example in order to facilitate testing, or to minimize the extent of any possible operations during reconditioning or recycling.